This invention relates generally to a powder coating composition and, more specifically, to a thermosetting, epoxy resin-containing, powder coating composition suitable for forming an electrically insulating, tightly adhering coat on a metal surface.
The use of a thermosetting powder coating composition for the formation of an insulating layer on a metal surface is known. One such a known coating composition includes an epoxy resin and a curing agent such as an acid anhydride, a phenol novolak resin or dicyanodiamide. While the known coating composition shows good adhesiveness to ferrous metal surface, it fails to give a tightly adhering layer on a non-ferrous metal surface such as on a surface formed of copper or brass. Further, the known coating composition has a problem because electrical insulation of a cured coat obtained therefrom tends to be degraded during use. In particular, when the coated layer is subjected to repeated large temperature changes, to moistened conditions or to high electric voltages, the electrical insulation thereof becomes gradually poor.